Damage Localization Research For Arch Bridges

In recent years, a great deal of lower rank roads have been rebuilt and expanded in company with the development of economy and traffic construction. It is very important to keep the safety of the bridges in service. A majority of bridges built in 1960's orl970's are aged or damaged in different degree, which results in the decreasing of the load carrying capacity due to overloading and corruption. Bridges in damage are increasing with years. If those bridges are broken down, the loss will be enormous. Therefore, it urgently motivates the development of the effective means to prevent the bridges form tragic events.In present, the extensively research attention has been drawn to the structural damage identification methodology based on dynamic test because of the global safety assessment and the cost-effectiveness. According to the measured data and identification principle, the identification methods can be divided into the method based on frequency, mode shape, mode curvature/strain mode, modal flexibility and modal strain energy and so on. Whereas, the errors of the components of the mode shapes often exceed 20% in the field test for the civil infrastructures, and the error of the frequency doesn't exceed 1.5%. It is a challenging task to identify the structural damage by using of the lower frequencies, which is available in practical test.A methodology of damage localization for the arch bridge based on frequency change square ration (FCSR) was presented by using of the lower frequencies in the dissertation. Firstly, the relationship between the local damage in the structure and the modal parameters is derived by the first order perturbation analysis. The damage-sensitive features based on FCSR was then proposed to localize the damage in arch bridge. Secondly, the numerical simulations were performed to investigate the validity of the proposed method. Finally, the experimental research was conducted to illustrate the effectiveness of the FCSR-based approach for the real structures. A organic-glass model of arch bridge was built in laboratory. The simulated damage was made by different depth notch, and the corresponding modal parameters were obtained. The damages in arch bridge model were localized by using of the lower frequencies. The results demonstrate that the proposed method can localize the structural damages for arch bridge, which can be applied to thesafety assessment.